The present invention relates generally to a portable terminal computer having an operation portion and an input/output portion, a main body connectable to a host computer for communication, and an optional unit connectable to the main body, and more particularly, the invention relates to a technique of safely and securely attaching and detaching the main body to and from the optional unit.
For example, a modem communication device which receives and transmits data between a portable terminal computer and a host computer through a telephone line is conventionally used as an optional unit for connection to a main body of the portable terminal computer. The modem communication device is connected to the portable terminal computer by a flat cable having male connectors at the opposite ends thereof and if necessary, it is mounted on the portable terminal computer at a protruding bracket by screws.
When carrying the modem communication device together with the main body of the portable terminal computer to a customer, for example, the modem communication device must be fixed to the bracket of the main body by screws, which makes the attachment and the detachment using a screw driver time consuming and troublesome. Furthermore, the flat cable with the male connectors and the bracket protruding from the main body hinder transport of the device and detracts from a uniform appearance. In addition, when carrying the modem communication device detached from the main body, the connectors and the flat cable are damaged causing imperfect contact of the connectors, resulting in malfunction of the main body or the modem communication device.
The conventional portable terminal computer also allows attachment and detachment of the modem communication device at any time while the main body is activated. Unless the main body is deactivated prior to the attachment and detachment of the modem communication device, the bus of the connector cannot be protected which might result in damage to the portable terminal computer. The operation of the modem communication device is therefore complicated. The attachment of the device requires three operations: power off, mounting, and power on; and the detachment thereof requires at least three operations: power off, dismounting, and power on. Careless modem attachment and detachment without turning off the power supply causes portable terminal computer malfunction or damage.